Spark gap tesla coil | SGTC

Spark gap tesla coil

Spark gap tesla coil or SGTC is a simple form of tesla coil that is capable of producing super high voltages in the output.

Big coils with high voltage input is very dangerous. So we are going to make a mini version of SGTC using bug zapper circuit. Once you are expert in handling high voltage then you can go for bigger design.

Components required for spark gap tesla coil

  1. High Voltage transformer ( bug zapper circuit )
  2. High voltage capacitor ( Approximately 5nf, > 2kv )
  3. 4v – 9v battery
  4. Primary coil ( 1mm insulated copper wire )
  5. Secondary coil ( 0.2mm magnet wire )
  6. Spark gap arrangement
  7. Alligator clips
  8. Some 0.5mm insulated connecting wires

High voltage transformer

This tutorial is for mini version of spark gap tesla coil. Small high voltage transformer can be found inside bug zapper ( mosquito racket ).

Take out the circuit from bug zapper along with its battery.

High Voltage Capacitor

High voltage capacitor of value approximately 5nf ( low capacity ) and 1 to 10 kv is difficult to find in market, So I made my own capacitor of 5nf and 10kv using aluminium foil and plastic sheets.

Spark Gap

Spark gap is basically an air gap that acts as switch. It switches on when capacitor gets charged enough to jump across the air gap.

Spark gap

I made it using PVC pipe of 50mm outer diameter and two pieces of one inch screw. The tip of both screw point each other as shown. I have used screw so the gap can be adjusted.

Primary coil

The primary coil comprises of 3 turns made using 1mm insulated copper wire.

Use 50mm diameter PVC pipe as core for primary.

Secondary Coil

Make 300 to 1000 turns of 0.2mm magnet wire around 30mm diameter PVC pipe ( as core ). Make coils ( turns ) one after another such that no turn should overlap. The length of pipe should get covered.

Top load

Top load can be made using lite weight aluminium structure. It will be good if It has smooth surface and no sharp corners.

Generally people wrap plastic ball inside aluminium foil for this purpose.

Circuit diagram

This is a general circuit diagram for Spark gap tesla coils.

Spark gap tesla coil

The bug zapper circuit is going to cover the bounded part of circuit diagram as shown.

Tesla coil using mosquito racket


The connections of circuit is quite simple as it has only few components.

  1. Take bug zapper circuit and connect its output point 1 & 2 ( shown in diagram ) to the terminals of high voltage capacitor. Here the bounded area of circuit is bug zapper circuit.
  2. Now connect first end of capacitor to one end of spark gap ( use alligator clips ).
  3. Connect the other end of spark gap to primary coil.
  4. Connect the other end of primary coil to point 2.
  5. Ground the lower end of secondary coil.
  6. Attach top load to Upper end of secondary coil.
  7. The secondary coil is placed inside of primary coil, such that primary coil surrounds secondary coil.

Safety Tip

Spark gap tesla coil produce super high voltage in the output that is very dangerous. Even a small design with low voltage input can cause harm.

Don’t touch the coil, circuit or sparks at top load with bare hands. Even after you turn off the circuit, there can be charges stored in capacitor that can shock you.

You can discharge the capacitor by shorting the spark gap.


Akash Sharma

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